In a printmaking device, sheet registration sensors are required to know the position and orientation of the sheet at various points in time, such as before the registration starts to know the initial errors to correct, after the registration to check registration errors or continuously throughout registration to do closed loop registration. It would be ideal to have sensors everywhere to know the sheet position and orientation at all times. But having a large number of sensors is not practical because of cost and space constraints in a printmaking device.
Currently, a limited number of sensors are used to register the sheet and check performance. These sensors are typically tailored to a given model or series of a printmaking device. When determining the sheet registration, center of mass information and other measurement information is initially based upon direct input (e.g., selecting A4, or 8½×14 inch sheet) or indirectly by adjustment of path guides or by sheet-size detectors. Thereafter, the position and orientation of a sheet is measured at various points in time and input into a control device, typically a computer processor that regulates the process elements of the feed path and informs the image controller.
Once sufficient information is obtained, the sheet registration is checked for registration errors periodically, or continuously in a closed-loop registration system. The problem with the current methods and systems using the limited number of sensors is that the information relating to the sheet position and the sheet orientation is not always available when needed. Therefore, it would be advantageous to provide a sheet observer system and method that utilizes mathematical models to accurately estimate the position and orientation of a sheet at all times based on limited sheet sensor readings to provide better registration performance.